[linux-audio-user] sounblaster live platinum and full-duplex recording (noisy)

[Lee Revell]

On Fri, 2004-08-13 at 23:30, Erik Steffl wrote:
>    recording seems to be working OK but:
> 
>    in audacity when I record the track it sounds OK
> 
>    however if I generate click track and record then (the click track is 
> playing while I am recording) the recording is really bad (noisy, low 
> quality).
> 
>    I vaguely remember something about full-duplex on sounblaster not 
> being very good, i.e. there's something wrong when using it but don't 
> remember what (bitrate being forced to be very low or something along 
> those lines).
> 
>    However I can't find any information on that subject now (I tried 
> google and creative site), does anybody know details and/or have some 
> pointers to relevant docs?
> 
>    system: debian unstable, 2.6.5 kenrel (with alsa), sounblaster live 
> platinum (with live drive).
> 

The hw:x,0 capture device on the sb live is not very good.  For good
results you have to use the hw:x,0 playback device and the hw:x,2
capture device.  You have to use 48khz.

To record at the lowest latencies you have to record more than 2
channels.  This is because the capture buffer size is fixed in bytes;
doubling the number of channels halves the amount of time between
interrupts with a fixed buffer size.

This did not work at all until very recently, I believe you need the
ALSA 1.0.6-rc1 release candidate.

Search the recent alsa-devel archives for 'emu10k1 low latency capture'
and 'emu10k1 multichannel' for more info.

Lee